1. Field of the Invention
The invention relates to a control device and a control method of a hybrid vehicle and, more particularly, to a technology that remedies the time delay from the activating operation until the vehicle becomes ready to run.
2. Description of the Related Art
There is a known type of hybrid vehicle equipped with a motive power distribution mechanism that distributes the output of an engine to a first motor-generator and to a driving wheel-side output shaft, and a second motor-generator that outputs power to the driving wheel-side output shaft via a stepped type transmission.
In the case where the engine is to be cranked by using the first motor-generator in a hybrid vehicle as described above, there is a need to cause the second motor-generator to generate reaction force. Therefore, prior to the cranking, the stepped type transmission is put into a power transmission-ready state by operating an electric hydraulic pump so as to supply a line pressure that serves as an original pressure of the hydraulic type friction engagement devices of the stepped type transmission. This operation is performed by, for example, a control device of a hybrid vehicle described in Japanese Patent Application Publication No. JP-A-2005-329787.
Ordinarily in the above-described hybrid vehicle, prior to the running of the vehicle, an activating operation of a hybrid control system is performed through a certain operation, for example, by operating an activation button while operating the brake after inserting the key into the slot. Then, the operation of hydraulic pumps, the operation of shift control valves, the operation of the hydraulic type friction engagement devices of the stepped type transmission, etc., are confirmed via hydraulic switches that detect the engagement oil pressure of the hydraulic type friction engagement devices. On the condition that the hydraulic switches have operated, a ready-to-run (RDY-ON) state is set. After the ready-to-run state is set, the vehicle is run by operating the shift lever to a run position and operating the accelerator pedal.
During the activating period following the activating operation, a procedure of confirming the operation of each of hydraulic switches by operating the individual hydraulic pumps sequentially so as to raise the line pressure from the non-working pressure of the hydraulic switch is performed in order to confirm the operation of each of the hydraulic pumps. However, due to the pulsation of the working oil pressure output from a hydraulic pump, the hydraulic switch may sometimes undergo a so-called hunting phenomenon in which the switch repeatedly turns on and off even though the oil pressure is relatively low, that is, at a non-working pressure level of the hydraulic sensor, if the pulsation of the working oil pressure exceeds a predetermined frequency.
During the activating period following the activating operation, when the engine is started up to operate the hydraulic pumps that are driven by the engine and simultaneously an oil pressure command regarding the line pressure is switched from the low pressure side to the high pressure side and the rise of the line pressure to the high pressure side is to be confirmed by the operation of the hydraulic switch, the malfunction by the hunting of the hydraulic switch can occur. Hence, the line pressure is held high for a certain period, and after a predetermined period elapses, a low pressure command is output for a predetermined period followed by the output of a high pressure command. After the operation of the hydraulic switch corresponding to the output of the high pressure command is confirmed, the ready-to-run state is set. Thus, there occurs a drawback of a prolonged time from the activating operation to the setting of the ready-to-run state, that is, a prolonged activating period following the activating operation. This drawback becomes more remarkable in the case where the engine rotation speed is made high, for example, at the time of fast idle rotation during the time of low temperature, or the like.